Directory UMM :Data Elmu:jurnal:E:Environmental Management and Health:Vol09.Issue4.1998:

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J.T. Ayo de le and M.B. Abubakar

Trac e e le me nt c o ntaminatio n o f rain wate r in the se mi-arid re gio n o f Kano , Nige ria Enviro nme ntal Manage me nt and He alth

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Results and discussion

T r a ce elem en t s in t h e a t m os p h er e exist in p a r t icu la t e for m a n d m ay b e r e ga r d ed in t h r ee r oles :

1 p ot en t ia lly t oxic p ollu t a n t s ; 2 n u t r ien t s ; a n d

3 t r a cer s of t r a n s fer m ech a n is m s.

T h es e elem en t s m ay b e s oil d er ived a s m a t er i-a ls blow n fr om t h e gr ou n d , t h e ocei-a n s, volca n ic er u p t ion s, in d u st r ia l a n d d om est ic p ollu t ion .

T h e r es u lt s for t h e m a xim u m , m in im u m , m ea n , t h e s t a n d a r d d ev ia t ion , et c. of t r a ce elem en t s in r a in w a t er a r e a s sh ow n in Ta ble I. T h ese con cen t r a t ion s a r e w it h in t h e

p r eva ilin g levels of m a n y ot h er in d u st r ia l cit ies (Fet h , 1967; Ter h a a r et a l., 1967; Gloeb el et a l., 1966). T h e con cen t r a t ion of t h ese m et a ls in t h e collect ed sa m p les w a s gen er a lly low exce p t for t h e ea r ly r a in s w h en h igh er va lu es w er e r ecor d ed . Met a l con cen t r a t ion s w er e in t h e or d er P b > Cu > N i > Cr > Cd > Zn , w it h t h eir levels p r ogr essively d ecr ea sin g w it h t h e fr eq u en cy of t h e r a in s. Ma xim u m con cen t r a -t ion of P b, Cr, Cu a n d N i w er e a b ove 1.1µg/ lit r e w h ile Zn a n d Cd w er e 0.10µg/ lit r e. E xce p t for s om e r a in s in J u ly / Au gu st , h igh -est P b con cen t r a t ion s w er e ob t a in ed a t t h e a ir p or t a n d a r ou n d t h e h eav y t r a ffic su b -st a t ion s. As a r es u lt of t h e w id e u ses of cop p er a n d lea d p r od u ct s, t h ey w er e p r esen t in a ll t h e r a in w a t er sa m p led .

E n v ir on m en t a l con t a m in a t ion by lea d is w id es p r ea d , t h e m a jor a n t h r op ogen ic sou r ce of t h is elem en t b ein g t h e com bu st ion of lea d ed ga solin e (Dim u ch ow sk i a n d By t n er ow -icz, 1995; Gh a u r i et a l., 1994; Koe p p e, 1981). Alt h ou gh it s u se h a s b een d is con t in u ed in som e cou n t r ies, t h e u se of t et r a a lk y l lea d com p ou n d a s a n t ik n ock a d d it ive r em a in s t h e la r gest a p p lica t ion of or ga n olea d com p ou n d s (H ew it t a n d H a r r ison , 1986). Veh icu la r Table I

Le ve ls o f trac e e le me nts in rainwate r (µg/ litre )

Lead Cadmium Chromium Copper Z inc Nickel

M aximum 1 .2 9 0 .1 1 3 0 .6 3 2 1 .1 6 8 0 .1 5 2 2 .2 7

M inimum 0 .0 5 1 0 .0 7 0 0 .1 1 3 0 .0 1 6 0 .0 0 2 0 .2 6 7

M ean 0 .6 0 5 0 .0 7 0 0 .2 6 7 0 .3 7 2 0 .0 5 4 0 .3 2 5

Standard deviation 0 .1 2 9 0 .0 2 2 0 .1 3 3 0 .0 4 6 0 .0 4 2 0 .1 8 3

CV (%) 2 1 .3 2 3 1 .4 3 4 9 .8 1 1 2 .3 7 7 7 .7 8 5 6 .3 1

Figure 1

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em is s ion s of t et r a a lk y lea d a r e s u b ject t o a t m os p h er ic b r ea k d ow n t o t r ia k y l- a n d d ia lk y lea d a n d a ll t h e t h r ee for m s a r e s cav -en ged fr om t h e a t m os p h er e by r a in fa ll (All-en et a l., 1988; H a r r is on a n d La k en , 1978; H ew it t a n d H a r r ison , 1986; Wellbu r n , 1988). T h a t t h e a t m os p h er ic m et a llic a er os ols, e.g. lea d , r em a in in a solu ble for m a s t h e h a lid e or s u lp h a t e h a s b een d em on st r a t ed by La zr u s et a l. (1970).

T h e r es u lt s of t h r ee-yea r s a m p lin g s t u d ies s u gges t t h a t t h e a n n u a l solu ble d e p osit ion m ay con t r ibu t e t o a n ot a ble p er cen t a ge of t h e ava ila ble fr a ct ion in t h e s oil in r es p ect of a n u m b er of elem en t s.

Un d er t h e in fl u en ce of t h e h a r m a t t a n w in d , cou p led w it h t h e h igh t em p er a t u r es r ea ch ed by s oils, a n d t h e st r on g d iu r n a l t h er m ic t u r -bu len ce r es u lt in g fr om t h es e d u r in g t h e d r y s ea s on , t h es e a r e fa ct or s w h ich favou r t h e p r od u ct ion of d u s t a n d it s s u s p en s ion in t h e a t m os p h er e, su ch t h a t t h e a ir p a r t icu la t e levels of m a n y elem en t s a r e in exces s of a n or d er of m a gn it u d e gr ea t er t h a n t h e levels

t h a t wou ld , u n d er n or m a l con d it ion s, b e r ecor d ed .

E lem en t s a ssocia t ed w it h in d u st r ia l p ollu -t ion a r e in cr ea sin g in con cen -t r a -t ion , e.g. lea d , ch r om iu m , cop p er a n d n ick el. T h u s, t h e effec-t iven ess of w a sh in g-ou effec-t a n d effec-t h e im p a ceffec-t ion of r em ov in g t r a ce elem en t s fr om t h e a t m osp h er e in Ka n o, w h er e t h e m ea n a n n u a l r a in -fa ll is 840m m , m ay n ot b e t ot a lly r ea lised . T h e h igh er con cen t r a t ion s of t r a ce m et a ls in t h e ea r ly r a in s m ay b e ow in g t o t h e a ggr e ga t ion of t h e m et a l p a r t icles in t h e a t m osp h er e. It m ay, h en ce, b e con clu d ed t h a t r a in fa ll a n d d r y sed im en t a t ion a r e t h e m a jor r ou t es for r em ov in g t r a ce m et a ls fr om t h e a t m osp h er e.

F igu r e 3 (a -f) sh ow s t h e d ist r ibu t ion for t h e t r a ce m et a ls in r a in w a t er. T h e r esu lt s exh ib it a r a n ge of con cen t r a t ion s b et w een t h e ea r ly a n d s u b seq u en t r a in s, su gges t in g st r on g sp or a d ic in fl u en ce fr om a n t h r op ogen ic sou r ces. Ch r om iu m is r elea sed in t o t h e a t m osp h er e fr om in d u st r ies su ch a s m et a l fi n ish in g, p igm en t s m a n u fa ct u r e, t ext iles, cer a m ics, t a n n er ies, et c. T h e h igh Cr

Figure 2

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Fet h , J .H . (1967), “Ch em ica l ch a r a ct er ist ics of bu lk p r ecip it a t ion in t h e M a jave Des er t r e gion Ca lifor n ia ”, Un ited S ta tes Geol. S u r v . P r of. P a p., N o. 575C, p p. 222-7.

Gh a u r i, B., Sa la m , M. a n d M ir za , M .I. (1994), “An a sses sm en t of a ir q u a lit y in Ka r a ch i, P a k -ist a n ”, E n v ir on . M on itor a n d A ssess, Vol. 32, p p. 37-45.

Gloeb el, B., M u t h , H . a n d Ob er h a n s en , E . (1966), “Up t a k e a n d excr et i on of n a t u r a l r a d i o-n u clei d es, lea d 210 a o-n d p olem i u m 210 i o-n m a n ”, S tra th len th era p ie, Vol. 13 N o. 2, p p. 218-26.

H a r r ison , R.M. a n d La k en , D.P.H . (1978), “A com -p a r a t ive st u dy of m et h od s for t h e a n a ly s is of t ot a l lea d in soils”, E n v ir on . S ci. T ech n ol., Vol. 12, p p. 1,384.

H ew it t , C.N. a n d H a r r ison , R.M . (1986), “For m a t ion a n d d ecom p osit ion of t r ia lk y l lea d com -p ou n d s in t h e a t m os-p h er e”, E n v ir on . S ci.

T ech ., Vol. 20, p. 797.

J on es, M.J . (1971), “Am m on iu m a n d n it r a t e n it r o-gen in t h e r a in w a t er a t Sa m a r u , N iger ia ”,

T ellu s, Vol. XXIII, p p. 459-61.

Koe p p e, D.E . (1981), “Lea d : u n d er s t a n d in g t h e m in im a l t oxicit y of lea d in p la n t s ”, in La p p, N.W. (E d .), E ffects of T ra ce M eta ls on Pla n t

Fu n ction , Ap p lied Scien ce P u blish er s, Lon

-d on , N J , p p. 55-76.

La zr u s, A.L., Lor a n ge, E . a n d Lod ge, J .P. (1970), “Lea d a n d ot h er m et a l ion s in Un it ed St a t es

p r ecip it a t ion ”, E n v ir on . S ci. T ech ., Vol. 4, p p. 19-22.

Lu n d h olm , B. (1979), “E cology a n d d u s t t r a n s-p or t ”, in M or a les (E d .),S a h a ra n Du st M ob

i-liz a tion , T ra n sp or t Dep osition , Scien t ifi c

Com m it t ee on P r oblem s of t h e E n v ir on m en t (SCOP E 14), p a p er s a n d r ecom m en d a t ion s fr om a wor k sh op h eld in Got h en bu r g Sw ed en , 25-28 Ap r il 1977, ch . 3, p p. 61-8.

Ter H a a r, G., H olt zm a n , R.B. a n d Lu ca s, H .F. (1967), “Lea d a n d lea d 210 in r a in w a t er ”, N a tu re, Vol. 216 N o. 5,113, p p. 353-5.

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Results and discussion

Further reading